Area Forecast Discussion
Issued by NWS Little Rock, AR

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705
FXUS64 KLZK 130544 AAB
AFDLZK

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
1145 PM CST Thu Jan 12 2017

.Aviation...

Overall VFR flight conditions with ceilings will start the forecast.
Overnight areas of MVFR ceilings will from as the cold front slowly
sags south overnight. Also light showers will be seen, especially
over northern and central AR. Temperatures will be around freezing
over far northern AR toward Friday morning, and patchy freezing
precip may be seen near KHRO and KBPK, but chance is too low to
include in Tafs. Otherwise winds will be north to northeast at 5 to
10 mph over northern to much of central AR, while until the front
sags through, winds will be south at 3 to 10 mph over southern AR.
(59)

&&

.PREV DISCUSSION...(ISSUED 246 PM CST Thu Jan 12 2017 )

SHORT TERM...Tonight Through Saturday

Southwest flow continues across Arkansas this afternoon. An upper
high is over the southeast and an upper low is over the California
coast. The upper low will move south to the Baja Peninsula by
Saturday. The upper high will remain stationary.

Current radar images show some showers developing along the cold
front and ahead of it. The chance of showers will continue through
the overnight hours. Much colder air is behind this front as well,
with temperatures in the 30s in the northwest and mid 70s in central
Arkansas. Moisture is expected to over run the front tonight and
bring light showers north of the front. Most places will remain
above freezing overnight...however areas along the Missouri border
could drop to freezing or a little below for 3-4 hours around
sunrise and create light freezing rain. No more than a few
hundredths of freezing rain is expected.

The front is expected to stall in southern Arkansas Friday morning.
Rain chances will continue over the area through Saturday.
Temperatures will be cooler through Saturday with mainly 40s and 50s
for highs Friday, and 50s and 60s Saturday.

LONG TERM...Saturday Night Through Thursday

At the beginning of the period, upper ridging will push quasi-
stationary boundary north and out of Arkansas, with maybe a brief
lull in precipitation chances. However, this will change by Sunday
night, as a negatively tilted trough associated with a closed upper
low in the panhandles region makes its way into the plains and mid
south. This will allow for scattered to numerous showers and
thunderstorms to develop Sunday night and Monday.

Showers/storms will continue into Monday night and Tuesday, as a
cold front makes its way into the state. However, the boundary will
hit upper ridging over the southeast conus and seriously slow down
or even stall out. Several upper level waves will move through in
the mean flow and interact with the front, with more showers/storms
into Monday night.

Monday night and Tuesday, the upper ridge over the southeast will
translate eastward, which will give the front a little nudge further
into the state. However, the boundary will likely slow down/stall
out again, with more waves interacting with it.

By Wednesday night/early Thursday, a stronger upper system should
give the front a push away from the region.

I`ll address forecast concerns below...

Strong storms...
Would not be surprised to see a strong storm or two on Sunday night
and Monday. There will be a high amount of shear present, however
surface-based instability, or lack thereof, will be an inhibiting
factor.

Confidence level...I`m going to go with low for now.

Heavy rainfall...
With the scenario discussed, several inches of rainfall are likely
over the course of several days. At this time, models disagree over
how much and where it will set up. Big surprise, right?

With the front slowing down or stalling out more than once, there
would likely be two axes of heaviest rainfall...one over the
northwest, and one over the southeast. However, with over all weak
steering flow during this time period, storms will be likely forming
and moving over the same areas (training in other words).

With the data I`m currently looking at, one to three inches of rain
seems to be a good bet over all of Arkansas. However, where the axis/
axes of heavy rainfall sets up, amounts could go over three inches,
which could lead to some flash flooding concerns, especially if the
front ends up taking more time to move across the state.

Confidence is fairly decent in terms of the heavy rain scenario.
Confidence in specific rainfall amounts is low at this time. My
concern is that models could be underdoing the heavier amounts,
given two source regions of moisture (low level Gulf flow, and
mid/upper level flow from the Pacific). Guess we will see.

&&

.LZK Watches/Warnings/Advisories...NONE.
&&

$$



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